Secondary Ion Mass Spectrometry Characterization Research Articles

Application of organic phosphonic acid dispersant in the separation and flotation of chalcopyrite and serpentine

The floatation of target minerals is often severely deteriorated in highly muddy mineral flotation systems. In this study, it was shown that the chalcopyrite recovery was significantly decreased due to the slime-coating of the serpentine fines. To enhance the floatability of chalcopyrite in the presence of serpentines, two phosphonic acids of 1-Hydroxyethylidene-1,1-diphosphonic acid (HEDP) and ethylenediamine tetramethylene phosphonic acid (EDTMP) were applied as dispersants in the floatation process. The micro-flotation tests indicated that HEDP and EDTMP could well eliminate the adverse effect of coated serpentine on the floatability of chalcopyrite. Adsorption tests and X-ray photoelectron spectra (XPS) analysis demonstrated that HEDP and EDTMP could selectively adsorb on the serpentine surface due to the chelation of phosphonic acid groups with the magnesium atoms on the serpentine surface, which was confirmed by the flight secondary ion mass spectrometry (TOF-SIMS) characterization. The zeta potential measurements showed that the adsorption of dispersants on serpentine changed the surface charges from positive to negative, while the zeta potential of chalcopyrite became more negative due to the dissolution of copper and iron cations from the chalcopyrite surface. Therefore, the electrostatic repulsion effectively prevented the slime-coating of serpentine on the chalcopyrite surface, which was also supported by the atomic force microscope (AFM) force measurements. As a result, the use of dispersants eliminated the adverse effects of serpentinite and greatly improved the floatability of chalcopyrite. The findings in this work indicate that the phosphonic acids of HEDP and EDTMP might find their application as effective dispersants to improve the floatability of target minerals in highly muddy mineral flotation systems.

Secondary ion mass spectrometry characterization of matrix composition in topological crystalline insulator [formula omitted

This study explores the use of Secondary Ion Mass Spectrometry (SIMS) to accurately measure the content of Pb1−xSnxTe, a new class of electronic materials known as Topological Crystalline Insulators (TCIs). We analyzed the SIMS signal ratios of SnCs+/PbCs+ and Sn±/Pb± in thin layers and determined the calibration curves necessary to estimate the exact amount of content in this ternary compound. Additionally, we investigated the matrix effect and performed depth profiling to obtain a more precise determination of the content. These findings contribute to the understanding and development of TCIs, and highlight the potential of SIMS for accurate content determination in ternary compounds.

Synergistic activation of smithsonite with copper-ammonium species for enhancing surface reactivity and xanthate adsorption

Copper ions (Cu2+) are usually added to activate the sulfidized surface of zinc oxide minerals to enhance xanthate attachment using sulfidization xanthate flotation technology. The adsorption of Cu2+ and xanthate on the sulfidized surface was investigated in various systems, and its effect on the surface hydrophobicity and flotation performance was revealed by multiple analytical methods and experiments. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) characterization demonstrated that the adsorption of Cu2+ on sulfidized smithsonite surfaces increased the active Cu—S content, regardless of treatment in any activation system. The sulfidized surface pretreated with NH4+–Cu2+ created favorable conditions for the adsorption of more Cu2+, significantly enhancing the smithsonite reactivity. Zeta potential determination, ultraviolet (UV)-visible spectroscopy, Fourier transform-infrared (FT-IR) measurements, and contact angle detection showed that xanthate was chemically adsorbed on the sulfidized surface, and its adsorption capacity in various systems was illustrated from qualitative and quantitative aspects. In comparison to the Na2S–Cu2+ and Cu2+–Na2S–Cu2+ systems, xanthate exhibited a higher adsorption capacity on sulfidized smithsonite surfaces in NH4+–Cu2+–Na2S–Cu2+ system. Hence, activation with Cu2+–NH4+ synergistic species prior to sulfidization significantly enhanced the mineral surface hydrophobicity, thereby increasing its flotation recovery.

Thin Films Fabricated by Pulsed Laser Deposition for Electrocatalysis

Thin Films Fabricated by Pulsed Laser Deposition for Electrocatalysis

Comprehensive Analysis of Phosphorus-Doped Silicon Annealed by Continuous-Wave Laser Beam at High Scan Speed.

We report an in-depth analysis of phosphorus (P)-doped silicon (Si) with a continuous-wave laser source using a high scan speed to increase the performance of semiconductor devices. We systematically characterized the P-doped Si annealed at different laser powers using four-point probe resistance measurement, transmission electron microscopy (TEM), secondary-ion mass spectroscopy, X-ray diffractometry (XRD), and atomic force microscopy (AFM). Notably, a significant reduction in sheet resistance was observed after laser annealing, which indicated the improved electrical properties of Si. TEM images confirmed the epitaxial growth of Si in an upward direction without a polycrystalline structure. Furthermore, we observed the activation of P without diffusion, irrespective of the laser power in the secondary-ion mass-spectrometry characterization. We detected negligible changes in lattice spacing for the main (400) XRD peak, showing an insignificant effect of the laser annealing on the strain. AFM images of the annealed samples in comparison with those of the as-implanted sample showed that the laser annealing did not significantly change the surface roughness. This study provides an excellent heating method with high potential to achieve an extremely low sheet resistance without diffusion of the dopant under a very high scan speed for industrial applications.

Petrographic, geochemical, and geochronological characteristics of metaplagiogranites from a high-pressure mélange in the Yuli belt, eastern Taiwan: Evidence for an early Miocene igneous precursor

Glaucophane-bearing metaplagiogranite occurs among the high-pressure (HP) metamorphic rock types poorly exposed in the Yuli belt. This lithologic association has been interpreted as scattered fragments of a metamorphosed ophiolite. Through field and petrographic investigations, we have identified several types of metaplagiogranite in the Chinshuichi area. This study reports the first U-Pb zircon dates by secondary ion mass spectrometry (SIMS) and whole-rock geochemical characterization of these metaplagiogranitic samples and associated metagabbro. The newly-obtained U-Pb zircon dates of 17.4–16.9 Ma are interpreted as magmatic crystallization ages. The δ 18 O averages of the dated zircon grains are 3.9–5.0 ‰ for the metaplagiogranites and 4.9 ‰ for the metagabbro, implying that the ultimate source rocks were of mantle origin. These metaigneous rocks are characterized by negative niobium tantalum anomalies in whole-rock composition. Protoliths of these HP metaigneous rocks may have formed in a nascent forearc setting related to an early Miocene subduction initiation. This finding infers that HP metamorphism of the Chinshuichi plagiogranite was caused by subduction erosion, and challenges some previous models that commonly postulated the South China Sea origin for the metaophiolitic fragments of the Yuli belt. • Four types of metaplagiogranite are newly identified. • First report of magmatic zircon ages of ~17 Ma by SIMS U-Pb dating on the metaplagiogranites. • Protoliths of the metaplagiogranites are likely forearc materials related to subduction initiation. • High-pressure metamorphism in the study area might have been partially caused by subduction erosion.

New SIMS method to characterize hydrogen in polysilicon films

A new analysis protocol for profiling the hydrogen (H) concentration depth distributions in polysilicon (poly-Si) thin films on Si oxide was developed by using secondary ion mass spectrometry (SIMS). Traditional SIMS determination of H concentrations in poly-Si films is to monitor and collect the atomic H−, but this analysis method presents some challenges for providing stable and repeatable H depth profiles, especially, for shallow profiling in thinner poly-Si films on thicker Si oxide films. In this paper, we present a thorough study of the SIMS characterization of H levels in poly-Si thin films on Si oxide. We describe an approach for the use of cluster SiH− instead of atomic H− to determine the H concentrations. The utilization of the SiH− cluster ion minimizes both H adsorption effects on the film surface regions and sample surface charging effects arising from the Si oxide layer underneath, thus enhancing the secondary ion signal stability in poly-Si films, as discussed with secondary ion energy distribution on the samples. This method differs from the conventional SIMS analysis of H in thin films and significantly improves the data quality and accuracy. Fourier transform infrared spectroscopy analysis was used to study the Si–H chemical bonding information for investigating the nature of the SIMS collected SiH− cluster ions. Both the H implant sample with no significant Si–H bonding and the poly-Si samples with high levels of H and the weak Si–H bonding exhibited strong SiH− secondary cluster ion intensities in our studies. This indicates the cluster ion signals arise from either the combination of Si and H ions through the physics formation process or weak chemically bonded Si and H.

Insight into structure-property relationship of organometallic terpyridine wires: Combined theoretical and experimental study

Recent development in combined theoretical and experimental analysis methods offer an attractive opportunity to investigate organometallic materials. The selection of optimally combined characterization techniques allows for an effective description and even prediction of structure-property relationship occurring in terpyridine (TPY) molecules. In this work, secondary ion mass spectrometry (SIMS), quantitative and qualitative characterization, hand-in-hand, with density functional theory (DFT) calculations, can aid analysis of the chemical stability and reactivity of organic compounds. A case study was based on the characterization of [M-(TPY)2]2+ complexes (M: Co/Fe) with specific organic and organometallic architectures. The SIMS mass spectra showed the step-by-step molecules fragmentation and the quantitative SIMS analysis allowed to predict its direction. Analysis of electron density, electrostatic potential visualization, and calculated bonds length and HOMO-LUMO energetic gap were employed to confirm the differences between the bond-breaking mechanism depending on the metal atom bound to the terpyridine. The combined DFT/SIMS approach was successfully used to assess the chemical stability of various isomers of the TPY compounds, and to determine the possible fragmentation pathways depending largely on the metal centre present within the TPY structure.

SIMS and HR-XPS characterization of lithiated graphite from the magnetic fusion device RFX-mod

Lithium wall conditioning has improved the performance of many magnetic fusion devices. Li conditioning in the RFX-mod device was performed by: (1) a single Li pellet injector and (2) a multi-Li pellet injector during He plasma discharges; (3) a Li evaporator after He glow discharge cleaning and He plasma discharge exposure. This report compares the spatial and depth distributions of Li deposited on polycrystalline graphite witness samples at different locations in RFX-mod and the elemental and chemical compositions of the resulting surfaces. The sample surfaces were analyzed ex situ using secondary ion mass spectrometry (SIMS) and high-resolution X-ray photoelectron spectroscopy (HR-XPS). The results showed that Li pellet injection provided a relatively uniform toroidal coverage while Li evaporation produced highly localized Li deposition. A Li 1s HR-XPS peak at 56.5 eV binding energy (BE) characteristic of lithium-intercalated graphite was only observed with the sample exposed to Li evaporation. All of the samples exhibited a HR-XPS C 1s peak at 285.1–285.2 eV BE that is largely attributed to hydrogenated graphite. This finding suggests that hydrogenation of fresh graphite occurs during He plasma discharge exposures. Our results have implications for density control and the selection of Li conditioning techniques in magnetic fusion devices.

Ex-situ SIMS characterization of plasma-deposited polystyrene near atmospheric pressure

Polystyrene-like coatings are synthesized by plasma near atmospheric pressure. Elucidating their chemical structure after exposure to ambient air could be very challenging because of the interference of surface-related phenomena, mainly post-polymerization oxidation and contamination. In this paper, we propose secondary ion mass spectrometry (SIMS) in molecular depth-profiling mode, combined to multivariate analysis, as a more reliable tool for their investigation as a function of the injected power. Indeed, the information provided by the inner layers is more representative of the film in growth. The SIMS approach is validated by complementary, surface-sensitive and bulk techniques: X-rays photoelectron spectroscopy (XPS) and infrared spectroscopy (IR). The SIMS results suggest that the high concentration of -CH3 groups in the polymer matrix, pointed out by IR, is due to branching and/or grafting of CH3· radicals to active sites (prevalently in position α, β, γ) along the aliphatic backbone, in addition to a significant fraction of trapped oligomers. The oligomer contribution is supported by an original study based on the molecular weight dependence of the sputtering efficiency. The overall experimental evidences indicate a milder fragmentation of the precursor at lower powers, leading to a higher conservation of the aromaticity and a lesser branched and/or cross-linked content.

Microscopic mechanism of carbon annihilation upon SiC oxidation due to phosphorus treatment: Density functional calculations combined with ion mass spectrometry

We report first-principles static and dynamic calculations that describe the microscopic mechanism of carbon annihilation due to phosphorus treatment upon silicon carbide oxidation. We identify the most stable form of phosphorus in the oxide as being fourfold coordinated with the dangling PO unit and find that the unit attracts carbon ejected from the interface, thus operating as a carbon absorber. This finding provides a possible microscopic reasoning for the annihilation of C-related defects at the interface. The secondary ion mass spectrometry and electrical characterization of interface state density are also performed to corroborate the theoretical finding above.

Effect of dual-dielectric hydrogen-diffusion barrier layers on the performance of low-temperature processed transparent InGaZnO thin-film transistors

Dual-dielectric SiOx/SiNx thin-film layers were used as back-channel and gate-dielectric barrier layers for bottom-gate InGaZnO (IGZO) thin-film transistors (TFTs). The concentration profiles of hydrogen, indium, gallium, and zinc oxide were analyzed using secondary-ion mass spectroscopy characterization. By implementing an effective H-diffusion barrier, the hydrogen concentration and the creation of H-induced oxygen deficiency (H-Vo complex) defects during the processing of passivated flexible IGZO TFTs were minimized. A bilayer back-channel passivation layer, consisting of electron-beam deposited SiOx on plasma-enhanced chemical vapor-deposition (PECVD) SiNx films, effectively protected the TFT active region from plasma damage and minimized changes in the chemical composition of the semiconductor layer. A dual-dielectric PECVD SiOx/PECVD SiNx gate-dielectric, using SiOx as a barrier layer, also effectively prevented out-diffusion of hydrogen atoms from the PECVD SiNx-gate dielectric to the IGZO channel layer during the device fabrication.

Iodine Doping of CdTe and CdMgTe for Photovoltaic Applications

Iodine-doped CdTe and Cd1−x Mg x Te layers were grown by molecular beam epitaxy. Secondary ion mass spectrometry characterization was used to measure dopant concentration, while Hall measurement was used for determining carrier concentration. Photoluminescence intensity and time-resolved photoluminescence techniques were used for optical characterization. Maximum n-type carrier concentrations of 7.4 × 1018 cm−3 for CdTe and 3 × 1017 cm−3 for Cd0.65Mg0.35Te were achieved. Studies suggest that electrically active doping with iodine is limited with dopant concentration much above these values. Dopant activation of about 80% was observed in most of the CdTe samples. The estimated activation energy is about 6 meV for CdTe and the value for Cd0.65Mg0.35Te is about 58 meV. Iodine-doped samples exhibit long lifetimes with no evidence of photoluminescence degradation with doping as high as 2 × 1018 cm−3, while indium shows substantial non-radiative recombination at carrier concentrations above 5 × 1016 cm−3. Iodine was shown to be thermally stable in CdTe at temperatures up to 600°C. Results suggest iodine may be a preferred n-type dopant compared to indium in achieving heavily doped n-type CdTe.

Time‐of‐flight secondary ion mass spectrometry of wet and dry chemically treated display glass surfaces

AbstractDisplay glasses meet the demands of the flat panel display industry vis‐à‐vis their composition, flatness, and forming processes. Here, we report the high‐resolution time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) characterization of Corning® EAGLE XG®, a widely used display glass, and subsequent chemometric analyses of these data. Samples analyzed included the as‐formed glass, fracture surfaces from remelt bars, and as‐formed surfaces subsequently exposed to process‐relevant treatments, including strong acids and bases, two industrial detergents, and an atmospheric‐pressure plasma treatment. Elemental signals in the positive ion ToF‐SIMS spectra respond to surface treatments. Acidic conditions leach non‐silica components from the surfaces, while basic treatments extract these species less efficiently. The detergents leave residues of Na+ and K+. The atmospheric pressure (AP) plasma treatment had little effect on the surface composition, while the melt surface differs significantly from the bulk fracture surface. Above ca. 75 m/z, the negative ion spectra are dominated by two series of homologous cluster ions with compositions of SinO2n+2Al− and SimHO2m+1H−. The presence of these clusters suggests that analogous structures exist at the near surface regions of the samples. In a series of multivariate curve resolution (MCR) analyses, two or three MCR components captured >95% of the variance in the data for these samples.

Exfoliation of black phosphorus in ionic liquids

We report the characterization and formation of sonication-assisted liquid phase exfoliation of bulk black phosphorus (BP) crystals with the incorporation of two representative ionic liquids (ILs) ([Emim][Tf2N] and [Bmim][Tf2N]) as green dispersing media was attempted, which resulted in stable dispersion of multi-layer BP flakes with unsuspected high oxidation resistance and chemical/structural integrity due to the presence of IL layer on top of BP flakes. There are two unveiled issues for the generation of BP dispersion in ILs. First, thin films of BP flakes can be simply prepared through our approach. Because self-oxidation of BP in ambient condition can be significantly minimized in ILs, vacuum filtration step can be adopted to produce BP thin films in ambient condition. Second, the binding of IL molecules on BP flakes has been firstly demonstrated by the time-of-flight secondary ion mass spectrometry characterization. In addition to the exploitation of ILs as the green solvents with less environmental harmfulness, IL-based exfoliation of BP might be easily scalable because harsh control of atmospheric oxygen and moisture is unnecessary in this approach.

Gradient Films of Pristine Graphene/Pyrene-Functional Copolymers with Janus Electrical Properties.

We describe the first preparation of polymer-supported pristine graphene thin films with dramatically different electrical conductivities on the top and bottom surfaces. Pyrene-functional stabilizers based on polystyrene or poly(methyl methacrylate) were first synthesized by copolymerization of their monomers with 1-pyrenemethyl methacrylate. Stable dispersions of pristine graphene nanosheets were prepared by sonication of graphite in chloroform solutions of the pyrene-functional copolymers. Vacuum filtration of the polymer-stabilized graphene dispersions through a porous PTFE filter produces films with an internal gradient in nanosheet concentration. This gradient graphene concentration results in an electrically conductive, graphene-rich surface on one side of the composite film and a nonconductive, polymer-rich surface on its other side. Electrical conductivities ranging from 60 to 194 S/m are measured on the graphene-rich surface, which are among the highest conductivities reported for pristine graphene/polymer composites. Through scanning electron microscopy and secondary ion mass spectrometry characterization, these films were found to contain three distinct layers: a polymer-rich top surface, a transition layer with a gradient in nanosheet concentration, and a buckypaper-like bottom layer consisting of densely packed, highly oriented graphene nanosheets. The gradient structure of these films and their Janus-like electrical conductivity has potential applications in graded coatings for radiofrequency and optical devices.

Al2O3 e-beam evaporated onto silicon (100)/SiO2 by ToF-SIMS

The authors report the positive and negative ion time-of-flight secondary ion mass spectrometry characterization of a thin film of e-beam evaporated alumina on a silicon substrate using Bi3++ primary ions at 50 keV, where this film prevents poisoning of a Fe catalyst in carbon nanotube growth. The positive ion spectrum showed a strong Al+ signal, while the negative ion spectrum showed strong peaks due to AlO−, AlO2−, AlO3H2−, and OH−.

Development of nanotopography during SIMS characterization of thin films of Ge1−xSnx alloy

This work presents a study of application of secondary ion mass spectrometry (SIMS) to measure tin concentration in Ge1−xSnx alloy with x higher than solid solubility ∼1%, i.e. well above the diluted regime where SIMS measurements usually provide the most reliable quantitative results. SIMS analysis was performed on Sn+ ion implanted Ge films, epitaxially deposited on Si, and on chemical vapor deposition deposited Ge0.93Sn0.07 alloy. Three SIMS conditions were investigated, varying primary beam ion species and secondary ion polarity keeping 1keV impact energy. Best depth profile accuracy, best agreement with the fluences measured by Rutherford backscattering spectrometry, good detection limit (∼1×1017at/cm3) and depth resolution (∼2nm/decade) are achieved in Cs+/SnCs+ configuration. However, applied sputtering conditions (Cs+ 1keV, 64° incidence vs. normal) induced an early formation of surface topography on the crater bottom resulting in significant variation of sputtering yield. Atomic force microscopy shows a peculiar topography developed on Ge: for oblique incidence, a topography consisting in a sequence of dots and ripples was observed on the crater bottom. This behavior is unusual for grazing incidence and has been observed to increase with the Cs+ fluence. Rotating sample during sputtering prevents this ripple formation and consequently improves the depth accuracy.

Plasma flux-dependent lipid A deactivation

This paper reports the influence of gas plasma flux on endotoxin lipid A film deactivation. To study the effect of the flux magnitude of reactive species, a modified low-pressure inductively coupled plasma (ICP) with O radical flux ∼1016 cm−2 s−1 was used. After ICP exposures, it was observed that while the Fourier transform infrared absorbance of fatty chains responsible for the toxicity drops by 80% through the film, no obvious film endotoxin deactivation is seen. This is in contrast to that previously observed under low flux exposure conducted in a vacuum beam system: near-surface only loss of fatty chains led to significant film deactivation. Secondary ion mass spectrometry characterization of changes at the film surface did not appear to correlate with the degree of deactivation. Lipid A films need to be nearly completely removed in order to detect significant deactivation under high flux conditions. Additional high reactive species flux experiments were conducted using an atmospheric pressure helium plasma jet and a UV/ozone device. Exposure of lipid A films to reactive species with these devices showed similar deactivation behaviour. The causes for the difference between low and high flux exposures may be due to the nature of near-surface structural modifications as a function of the rate of film removal.

Low energy SIMS characterization of passive oxide films formed on a low-nickel stainless steel in alkaline media

Low-energy secondary ion mass spectrometry (SIMS) was used to study the oxide films formed on a low-nickel austenitic stainless steel (SS), potential replacement to conventional AISI 304 SS in reinforced concrete structures (RCS) that are subjected to aggressive environments. The effect of carbonation and the presence of chloride ions were studied. The oxide films formed a chemically gradated bi-layer structure with an outer layer predominately constituted by iron oxides and an inner layer enriched in chromium oxides. Chloride ions were not found in the oxide film but did have an effect on film structure and thickness.